Alzheimer's Disease Genetics

Alzheimer's disease is a common disorder affecting the central Nervous system and the brain, and has been found to be a common cause of dementia.

The basic mechanism in this disease is the formation of plaques on the brain. The amyloid cells are broken down by the enzyme beta-secretase in to smaller cells. These smaller cells then keep on accumulating and piling on each other and then finally the brain gets covered with these plaques. Theses plaques lead to the Alzheimer's disease. There are various stages of this disease, like the initial loss of intelligence. The patient loses the ability for abstract thinking, judgment, and solving of problems.

Next it progresses to Memory impairment, where events of recent happening are forgotten.

Next it progresses to the changes in personality and also in emotional outlook. All these are the late changes in the progress of the disease.

The Alzheimer's disease is not a simple process. It involves many complex factors like multiple genetic defects or mutations in the genes. These mutations can be either hereditary and passed on from generation to generation. Or it may be acquired through increased susceptibility, which in turn may be due to various other factors.

The genomics or the study of the genetic progress of the disease has revealed that the Alzheimer's disease is caused due to the aging process. The aging process either accelerates the damage of the brain cells or when the person is exposed to deleterious environmental processes. The intake of certain drugs can also cause the harmful effect.

The multiple defects in the genes are at the following mutational loci (APP, PS1, TAU, PS2) and many other different susceptibility loci (APOE, AACT, A2M, TNF, BACE, BCHE, NOS3, GSK3B)

All these loci are spread across the human genome and they all meet together to effect the deleterious changes. The combined effects of these loci lead to untimely and premature death of the neurons. The neurons are the brain cells and thus it leads to death of the brain cells. This is the mechanism of loss of function of these cells and a resultant psychiatric disease.

The damage to the neurons are in various forms like aberrations in the protein content of the mitochondria, formation of protofibrils, altered function or dysfunction of the ubiquity-proteasome system, injury to the mitochondria, piling up of folded proteins, reactions which not only excite the system but also are toxic, stress etc.

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